In, for example, an articulated robot (hereinafter, referred to as manipulator) a problem arises in that torque saturation occurs because the torque of a joint drive motor (hereinafter, referred to as motor) is consumed by gravity torque acting on a joint portion due to gravity and that vibration remains when positioning is carried out. To overcome this problem, acceleration and/or deceleration (hereinafter, referred to as acceleration/deceleration, and the speed of acceleration/deceleration is referred to as acceleration/deceleration) must be adjusted in consideration of the effect of gravity acting on respective joints of the articulated manipulator.
Heretofore, there is proposed a method of calculating gravity torque in real time according to an attitude of a manipulator and canceling the effect of gravity feed-forwardly (refer to Patent Document 1). In the method, gravity torque acting on a joint is calculated from the attitude information of the manipulator, and the effect of gravity is cancelled by subtracting the gravity torque from a drive torque command of a motor. Further, there is also proposed a method of adjusting an acceleration/deceleration time constant based on a calculation formula derived from a motion equation using the position of a teaching point of a manipulator, the attitude of the manipulator, the drive directions and drive speeds of respective axes (refer to Patent Document 1).    [Parent Document 1] Japanese Unexamined Patent Application Publication No. 10-244482    [Parent Document 2] Japanese Unexamined Patent Application Publication No. 7-261822